Technical Abstract:
WEBB, KIMBERLY M.*, PAUL COVEY, BRETT KUWITZKY, AND MIA HANSON, USDA-ARS, Sugar Beet Research Unit, 1701 Centre Ave., Fort Collins, CO 80526. Characterization of a population of Fusarium oxysporum, from sugar beet, using the population structure of putative pathogenicity genes.
Fusarium oxysporum f. sp. betae is an important pathogen in sugar beet (Beta vulgaris L.) which can lead to reductions in root yield, sucrose percentage, and juice purity. F. oxysporum f. sp. betae can be highly variable in growth, pigmentation, conidial production, and in virulence. Additionally, high rates of F. oxysporum isolated from symptomatic sugar beet are actually non-pathogenic. Many methods have been used to characterize the genetic diversity of F. oxysporum f. sp. betae from sugar beet however many of these technologies do little to describe regional populations of F. oxysporum f. sp. betae and are unable to differentiate between pathogenic F. oxysporum f. sp. betae and non-pathogenic isolates of F. oxysporum. F. oxysporum utilizes a wide array of secreted molecules, called effectors, and pathogenicity genes, which encode host determining factors that are used by the pathogen to cause disease in sugar beet. Utilizing these target effectors, it is possible to utilize patterns of nucleotide diversity (both within and among populations) to infer the molecular basis of pathogen relatedness. In this work, we obtained the nucleotide sequence for thirteen putative effectors, and characterized their diversity in the population from thirty isolates of F. oxysporum originally collected from symptomatic sugar beet. Using this information, we characterized the pathogen population by “clade” and “pathogenicity” to 1) determine the genetic diversity of the F. oxysporum population from symptomatic sugar beet and 2) determine if this diversity could be correlated to “pathogenicity” or “clade” designations of F. oxysporum f. sp. betae. We determined that eight genes were able to significantly describe the F. oxysporum population to “clade” and that five genes were significantly able to describe the population to “pathogenicity”.